#include<stdio.h>
int main(){
	int n;
	while(scanf("%d",&n)!=EOF)
	{
	if(n>=90){printf("A\n");}
	if(n>=80&&n<90){printf("B\n");}
	if(n>=70&&n<80){printf("C\n");}
	if(n>=60&&n<70){printf("D\n");}
	if(n<60){printf("E\n");}
	}
	return 0;
}
